The present invention relates to a road traffic simulator for performing a simulation regarding the traffic by running autonomously a vehicle that simulates a real vehicle behavior in a simulated road environment on a computer.
In planning a road traffic system, it is important to make an assessment in advance as to what effect can be expected from a specific plan relating to a part or whole of the traffic system (for example, likelihood of traffic jam). Accordingly, there has been conventionally developed a micro traffic simulation system that replicates a behavior of a vehicle on a computer to simulate the conditions of the traffic flow and/or the traffic jam to assist designing or assessment of a road traffic system.
In a typical micro traffic simulation apparatus, a speed or acceleration of a vehicle is calculated to update a location of the vehicle according to such detailed rules as: (1) when there are no other vehicles in front of the subject vehicle, the subject vehicle travels freely according to a speed limit of a lane or a speed set for the vehicle; (2) when there is another vehicle, an obstacle or a traffic light in the traveling direction of the subject vehicle, the subject vehicle accelerates, decelerates or stops in accordance with the speed or distance relative to such object in front of it; and (3) in case of turning to right or left, passing an obstacle and changing lanes, the subject vehicle takes a predetermined behavior as long as a relation with an oncoming car on an opposite lane, an obstacle or the like is in conformance with a predetermined condition.
According to such typical micro traffic simulation apparatus, since a car speed and acceleration is calculated for predetermined conditions, it is hard to simulate behaviors of an actual vehicle driver with respect to operation of a steering wheel, accelerator pedal and braking pedal. Likewise, behaviors of a car resulting from such driver's behaviors cannot be adequately simulated.
The Japanese Patent Application Unexamined Publication (Kokai) No. H11-272158 discloses a technique for preparing minute coordinates in order to incorporate a driving simulator that has a higher degree of freedom than a micro traffic simulation apparatus. But, it does not include details of vehicle behaviors.
Besides, the Japanese Patent Application Unexamined Publication (Kokai) No. 2002-157673 discloses a road traffic simulation system in which a specific vehicle among the vehicles under simulation is assigned as a driving simulation vehicle so that a traffic simulation function and the assigned vehicle can exchange necessary information. In this traffic simulation system, a person under test is requested to use the driving simulator to drive the simulation vehicle repeatedly in various traffic conditions so that the information about the environmental conditions and the driver's operations under those conditions can be obtained. Based on the obtained information, a driving behavior model is generated and the generated model is reflected to the vehicle behavior model for a simulation vehicle of the traffic simulation apparatus. By running the simulation vehicle based on this model, it is possible to realize a simulator in which the behavior of the simulation vehicle in various traffic environments can be simulated in detail.
However, the position of the vehicle in the micro traffic simulation apparatus is updated in accordance with the acceleration and/or speed in the forward/backward directions and a selected traveling lane. As a result, the vehicle travels along a predetermined track.
According to the traffic simulation apparatus of H11-272158, a vehicle can travel over any position on the road because the behavior of the vehicle generated by the driving simulator connected to the traffic simulation apparatus is defined with distance and angle. However, the positions of other vehicles are confined to their predetermined track because their positions are updated in accordance with the lane number and acceleration. Accordingly, it is not possible to simulate in detail the lateral fluctuation of the vehicle within a lane and various tracks in a road crossing.
In the system of the Kokai 2002-157673, a vehicle is divided into a vehicle and a driver. The driver's steering, accelerating and braking operations are incorporated into a driver model. However, with this model, freedom of the driver's behavior is rather small because the model is relatively simple. Besides, as to the vehicle, the disclosed system uses a vehicle model database in which the relations of driver behaviors and vehicle behaviors caused with the driver behaviors are described. Accordingly, the vehicle behaviors are limited to the behaviors described in the database. This approach cannot simulate the conditions which are not described in the database.
Thus, there exists a need for such road traffic simulation apparatus that can perform a vehicle simulation with a higher freedom of behaviors without pre-classifying the traffic environments and pre-defining the traveling rules to cope with the pre-classified environments.